Mono is a platform for running and developing applications based on the ECMA/ISO Standards. Mono is an open source effort led by Novell. Mono provides a complete CLR (Common Language Runtime) including compiler and runtime, which can produce and execute CIL (Common Intermediate Language) bytecode (aka assemblies), and a class library. . This package contains the Core Library (mscorlib.dll) of Mono which is the glue between the BCL (Base Class Libraries) and the JIT.